Impact of Ice-Shelf Estuaries on Ice-Shelf Surface Drainage Efficiency

Abstract:

The first known ice-shelf estuary was recently discovered on the Petermann Ice Shelf in northwest Greenland. Prior to this discovery, observations suggest that surface hydrology impacts ice-shelf stability via two mechanisms: pond formation which promotes instability, and river formation that might mitigate against instability. Remote sensing investigation of the Petermann Ice Shelf suggests that the Petermann Estuary enhances fracturing along the ice shelf and may therefore be a previously unconsidered ice-shelf surface hydrologic process that can destabilize an ice shelf. In particular, the impact of estuary formation on large-scale ice-shelf surface drainage efficiency remains uninvestigated. This is important, because an estuarine-induced reduction in surface drainage efficiency may increase surface meltwater ponding, potentially inducing flexure and fracture. To investigate this potential feedback, we use the time-series of ArcticDEM photogrammetrically derived ice-shelf surface elevation models, corrected using ICESat-2 mappings of exposed bedrock along the ice-shelf margin, to track changes in hydraulic flow gradients since the current estuary first formed in 2012. We account for the potential impact of ocean tides on surface drainage efficiency using tidal amplitude data from the CNES FES2014 tide model, and assess potential surface loading using estuary water volumes estimated from bathymetric mappings from ICESat-2 and ArcticDEM (when the channel is dry). Finally, we compare changes in surface hydraulic gradients, and thus surface drainage efficiency, with high-resolution satellite time-series records of estuary formation and evolution.